Description
The cost of Rubber Modified Asphalt Concrete (RUMAC) is currently 1.5 to 2 times the cost of conventional AC. Thus, from cost effectiveness point of view, the thickness of the RUMAC layer must be at least 1.5 to 2 times thinner than that of an AC layer. Analyses of pavement performance with RUMAC and conventional AC are presented. They are based on two principal types of distress, fatigue cracking and rutting, and include two traffic levels and three categories of subgrade stiffness. In general, RUMAC mixes behave better than conventional AC mixes. For similar performance in terms of fatigue cracking, it was found that: (a) The equivalency factor between RUMAC and conventional AC mixes is better than 1:1.35 (1 mm of RUMAC is equivalent to 1.35 mm of AC); (b) In order to maintain the same strain at the top of the subgrade, it is necessary to increase the subbase layer thickness to compensate for the reduction of the asphalt layer. The compensation factor between subbase and RUMAC layers is 1.33:1 (1.33 mm of subbase material is required for compensating for 1 mm reduction of asphalt). It is shown that pavements with RUMAC exhibit better resistance to rutting than those with AC materials.
